Sound-recording system



Feh 5 1929.,

T. J. ENGEL SOUND RECORDING SYSTEM Filed Jan. 30, 1928 7 Patented Feb.5, 1929.

UNITED STATES PATENT OFFICE- THEODORE J. ENGEL, OF BAYSIDE, NEW YORK,ASSIGNOR T BELL TELEPHONE LABO- RATORIES, INCORPORATED, OF NEW YORK, N.Y., A CORPORATION OF NEW YORK.

SOUND-RECORDING- SYSTEM.

Application filed January 30, 1928. Serial No. 250,411.

This invention relates to optical speech recording mechanisms andparticularly to automatic film changing devices associated. with suchrecording mechanisms.

In recording acoustically modulated light waves onphotographicallysensitive film it is desirable to record the light waves regardless ofthe duration of the speech or musical number without losing any of therecord.

The time required to record the average speech or musical number issometimes longer than the time required for the running of a film ofstandard length. This results in a loss of part of the record unlessmeans are provided to instantaneously shift the recording operation to anew film.

An object of. the invention is to accurately transfer tophotographically sensitive film a record corresponding to a series ofsuccessively occurring sound or picture variations.

A further object is to accurately record on several lengths of motionpicture film a continuous record of successively occurring acousticallymodulated light waves or picture variations withoutlosing any part ofthese records in transferring the recording operations from one lengthof film to another.

In accordance with the invention the above objects are accomplished bythe use of an electric circuit comprising a plurality of re lays tocontrol the operation of the motors which drive the film and to controlthe shutters of the recordng mechanism to admit or reject the lightwaves projected to the recording films. More specifically the inventionemploys two recording systems each comprising a film magazine with itsassociated lens, shutter, and a motor to drive the film. A single sourceof modulated light common to both systems is usedand consists of a lightsource, a light valve and spherical lenses to project the image of thelight valve on to the recording films. The light is directed to each ofthe recording films by two silvered reflecting prisms which divide thelight and reflect it to each of the films. An electric circuitcomprising a plurality of relays interconnects the driving motors andthe shutters. When the run of one standard length film is nearlycompleted a notch in the edge of the film engages a roller which closescircuits to operate the relays so as to close the driving motor circuitfor thesecond film. When this motor attains the proper speed a notch inthe edge of the second film engages another roller which closes anelectric circuit to stop the motor of the first film and open theshutter of the second film. With a mechanism of this kind-there is noloss of time in transferring from one film to another which thereforegives a complete record of the picture variations and their accompanyingmusical number;

Fig. 1 is a diagrammatic view of the apparatus and circuit connections.

Fig. 2 is a detail of the filmand its associated tripper contacts.

Referring to Fig. 1, a light source 3 projects light rays to a sphericallens 4, then to light valve 5. Voice modulated currents from microphonecircuit 20 are supplied to said light valve, thus varying the amount oflight transmitted in accordance with the speech currents.

- A preferred form of light valve is disclosed in Patent 1,638,555,August 9, 1927, to E. C. Wente. These acoustically modulated light wavespass through lens 6 and are then divided and reflected, by silveredreflecting prisms 7, toward each of the sound recording cameras 1 and 2.

The two cameras being alike, it will simplify the description toconsider only camera 2 for the present. This sound recording cameraconsists of casing 14. spherical lenses 9 and 12, film F film windingreels 15 and the film driving motor M Included in casing 14; are magnet70 for controlling the shutter 11, and contacts R and R associated withthe film for controlling the various switching operations.

Scenic cameras 26 and 27 record the action accompanying the speech ormusical number and although necessary for a complete description theyform no part of this invention.

The operation of the device is as follows:

Let it be assumed that both the sound recording mechanismsare at astandstill. If the operator wishes to start camera 2 he depresses key Dwhich energizes relay 40 through contact 19 of relay 4:5, battery E ofthe key D is only momentary, a locking means is provided for relay 40,the circuit comprising armature 17 relay 40, armature 19, battery E andground.

The shutters 11, 34, 10 and 35 are all connected in parallel circuit andeach pair is so mechanically adjusted that when 11 and 34 are open 10and 35 are shut and vice 'versa. Any switching operation affecting oneset I will afiect the other set. The shutters operate on the well knownprinciple of the ordinary camera shutter set on time exposure whereintwo operations of the shutter lever are necessary to open and close theshutter.

The film F is now recording the acoustically modulated light waves. Whenfilm F nears the end of its run, an indentation in film by engagingtripper R, (equivalent to R shown in Fig. 2) closes contacts to energizerelay 50 through battery E armature 23, relay 50 and ground. Armature 25attracted by relay 5O closes the circuit to heavy duty relay 60, whichattracts armature 28 closing the circuit to film driving motor M andpower supply lines 30. The film F, has an indentation H about four feetfrom the starting end of the film adapted to receive tripper B, (Fig.2). This tripper R falling into indentation H makes a double contact.Contact 29 closes the circuit to magnets 70, 75, 80, 85 through battery,windings of the magnets, contact 29, armature 18 and ground,

which opens shutters 10 and 35 and closes the shutters 11 and 34 of thefirst machine. Contact 31 closes circuit to relay 45 which attractsarmature 19, thus breaking the looking circuit of rela 40. Armatures 16,17 and 18 are release The release of armature 16 breaks the circuit ofmotor M thereby causing the film F to stop. The double contactcontrolled by R is so ad'usted that the contact 29 closes slightly eforecontact 31 because contact 29 closes the circuit to the magnet througharmature 18, to trip the shutters, and contact 31 closes the circuit torelay .45 which attracts armature 19 to break the locking circuit ofrelay 40, thereby releasing armae ture 18 from its contact. Therefore,it is necessary that the circuit through armature 18 be made before thesecond contact 31 opens the circuit.

It is obvious from the above description of the operation that eithermachine may be started first and the transfer from one machine to theother may be efiected without loss of any of the record, therebyeliminating the objections heretofore experienced in recording a musicalor speech program on photographically sensitive film.

IVhat is claimed is:

1. In a recording system, a source of acoustically modulated lightwaves, a photographically sensitive film, a second photographicallysensitive film, means for driving each of the films, means to projectlight waves from said source toward each of said films to produce aphotographic sound record, and means controlled by said films to shutoff said light waves from the first mentioned film and to Iproject saidlight waves upon said second 2. In a recording system, a source ofacoustically modulated light waves, a photographically sensitive film, asecond photographically sensitive film, driving means for each of saidfilms, means to project light waves from said source toward each of saidfilms to produce a photographic sound record, and automatic meanscontrolled by said films for alternately starting and stopping each ofsaid film drivmg means.

3. In a recording system, a source of acoustically modulated lightwaves, a photographically sensitive film, a second photographicallysensitive film, driving means for each of said films, reflecting prismsfor projecting light waves from said source toward each of said films toproduce a photographic sound record, and film controlled electromagnetic'means for starting one of said film driving light controllingmeans-with said driving' means.

5. In a recording system, a photographically sensitive film, a secondphotographically sensitive film, film controlled shutters associatedwith each of said films, a source of acoustically modulated light wavescommon to both of said films, means to project light waves from saidsource upon each of said films to produce a photographic sound record,

said light waves being admitted to either of said films under thecontrol of said film con trolled shutters.

6. In a recording system, a photographically sensitive film, a secondphotographically sensitive film, a source of acoustically modulatedlight waves common to both of said films, separate driving means foreach of said films, shutters associated with each of said films, saiddriving means and said shutters being simultaneously controlled by saidfilms. a photographic sound record, shutters asso- 7. In a recordingsystem, a source of acousciated with said films and means controlledtically modulated light waves, a photographiby said film to alternatelyopen and close each 1 cally sensitive film, a second photographically ofsaid shutters.

5 sensitive film, driving means for each of said In witness whereof, Ihereunto subscribe films, means to project light waves from said my namethis 28th day of January, 1928; source toward each of said films toproduce THEODORE J. ENGEL.

